<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>GROOPS - gravityfieldType</title>

    <!-- JQuery and Popper -->
    <script src="https://code.jquery.com/jquery-3.4.1.slim.min.js" integrity="sha384-J6qa4849blE2+poT4WnyKhv5vZF5SrPo0iEjwBvKU7imGFAV0wwj1yYfoRSJoZ+n" crossorigin="anonymous"></script>
    <script src="https://cdn.jsdelivr.net/npm/popper.js@1.16.0/dist/umd/popper.min.js" integrity="sha384-Q6E9RHvbIyZFJoft+2mJbHaEWldlvI9IOYy5n3zV9zzTtmI3UksdQRVvoxMfooAo" crossorigin="anonymous"></script>

    <!-- Bootstrap -->
    <!-- https://getbootstrap.com/docs/4.1/examples/ -->
    <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.min.js" integrity="sha384-wfSDF2E50Y2D1uUdj0O3uMBJnjuUD4Ih7YwaYd1iqfktj0Uod8GCExl3Og8ifwB6" crossorigin="anonymous"></script>
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.min.css" integrity="sha384-Vkoo8x4CGsO3+Hhxv8T/Q5PaXtkKtu6ug5TOeNV6gBiFeWPGFN9MuhOf23Q9Ifjh" crossorigin="anonymous">

    <!-- Mathjax -->
    <script type="text/x-mathjax-config">
    MathJax.Hub.Config({tex2jax: {inlineMath: [ ['$','$'] ],
                                  displayMath: [ ["\\[","\\]"] ],
                                  processEscapes: true},
                        TeX:     {Macros: {M: ["{\\mathbf #1}",1]},
                                  equationNumbers: {autoNumber: "all"}  }});
    </script>
    <script async src="https://cdn.jsdelivr.net/npm/mathjax@2.7.7/MathJax.js?config=TeX-AMS_CHTML" integrity="sha384-e/4/LvThKH1gwzXhdbY2AsjR3rm7LHWyhIG5C0jiRfn8AN2eTN5ILeztWw0H9jmN" crossorigin="anonymous"></script>

    <!-- lunr -->
    <script src="https://cdn.jsdelivr.net/npm/lunr@2.3.8/lunr.min.js" integrity="sha384-vRQ9bDyE0Wnu+lMfm57BlYLO0/XauFuKpVsZPs7KEDwYKktWi5+Kz3MP8++DFlRY" crossorigin="anonymous"></script>

    <!-- Mustache -->
    <script src="https://cdn.jsdelivr.net/npm/mustache@4.0.1/mustache.min.js" integrity="sha384-0PLEZVBpOQ+Kqw3anJWSNWvRxpEFt02tSpBvyRsA4WcvX/OTldWdXxGLVLvh954H" crossorigin="anonymous"></script>

    <!-- GROOPS Stylesheet -->
    <link rel="stylesheet" href="static/groops.css"/>

    <!-- icon -->
    <link rel="icon" href="static/groops_icon.png">

</head>
<body>
    <header>
        <nav class="navbar navbar-expand-lg navbar-dark bg-dark">
            <div class="container">
              <a class="navbar-brand" href="index.html"><img class="logo" src="static/groops_white.svg"></a>
              <div class="collapse navbar-collapse" id="mainNavbar">
                <ul class="navbar-nav mr-auto">
                  <li class="nav-item">
                    <a class="nav-link" href="programType.html">Programs</a>
                  </li>
                  <li class="nav-item">
                    <a class="nav-link" href="classes.html">Classes</a>
                  </li>
                  <li class="nav-item">
                    <a class="nav-link" href="general.parser.html">Parser</a>
                  </li>
                  <li class="nav-item">
                    <a class="nav-link" href="general.fileFormat.html">File Formats</a>
                  </li>
                </ul>
              </div>
                <form class="form-inline my-2 my-lg-0" action="search.html" id="searchTools">
                  <input class="form-control mr-sm-2" placeholder="Search" name="searchTerms" method="GET" value="" type="text" id="searchBox">
                  <button class="btn btn-secondary my-2 my-sm-0" type="submit" id="searchButton">Search</button>
                </form>
              <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#mainNavbar" aria-controls="mainNavbar" aria-expanded="false" aria-label="Toggle navigation" style="">
                <span class="navbar-toggler-icon"></span>
              </button>
            </div>
        </nav>
    </header>
    <main class="container px-0 pt-2 top-buffer">
        <div id="content" class="container">
            
<h1 id="gravityfieldType">Gravityfield</h1><p>
This class computes functionals of the time depending gravity field,
e.g potential, gravity anomalies or gravity gradients.</p><p>If several instances of the class are given the results are summed up.
Before summation every single result is multiplicated by a <strong class="groops-config-element">factor</strong>.
To subtract a normal field like GRS80 from a potential
to get the disturbance potential you must choose one factor by 1
and the other by -1. To get the mean of two fields just set each factor to 0.5.</p><p>Some of the instances gives also information about the accuracy.
The variance of the result (sum) is computed by means of variance propagation.
</p>

<h2 id="potentialCoefficients">PotentialCoefficients</h2><p>
Reads coefficients of a spherical harmonics expansion from file.
The potential is given by
\[
V(\lambda,\vartheta,r) = \frac{GM}{R}\sum_{n=0}^\infty \sum_{m=0}^n \left(\frac{R}{r}\right)^{n+1}
  \left(c_{nm} C_{nm}(\lambda,\vartheta) + s_{nm} S_{nm}(\lambda,\vartheta)\right).
\]If set the expansion is limited in the range between <strong class="groops-config-element">minDegree</strong>
and <strong class="groops-config-element">maxDegree</strong> inclusivly. The computed result
is multiplied with <strong class="groops-config-element">factor</strong>. If <strong class="groops-config-element">setSigmasToZero</strong> is true
the variances are set to zero. This option is only important for variance propagation
and does not change the result of the gravity field functionals.
</p>
<table class="table table-hover">
<tr class="table-primary"><th>Name</th><th>Type</th><th>Annotation</th></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset">inputfilePotentialCoefficients</div></div></td><td>filename</td><td></td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">minDegree</div></div></td><td>uint</td><td></td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">maxDegree</div></div></td><td>uint</td><td></td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">factor</div></div></td><td>double</td><td>the result is multiplied by this factor, set -1 to subtract the field</td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">setSigmasToZero</div></div></td><td>boolean</td><td>set variances to zero, should be used by adding back reference fields</td></tr>
</table>

<h2>PotentialCoefficientsInterior</h2><p>
Reads coefficients of a spherical harmonics expansion (for inner space) from file.
If set the expansion is limited in the range between <strong class="groops-config-element">minDegree</strong>
and <strong class="groops-config-element">maxDegree</strong> inclusivly. The computed result is multiplied with <strong class="groops-config-element">factor</strong>.
If <strong class="groops-config-element">setSigmasToZero</strong> is true the variances are set to zero.
This option is only important for error propagation
and does not change the result of the gravity field functionals.
</p>
<table class="table table-hover">
<tr class="table-primary"><th>Name</th><th>Type</th><th>Annotation</th></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset">inputfilePotentialCoefficients</div></div></td><td>filename</td><td></td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">minDegree</div></div></td><td>uint</td><td></td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">maxDegree</div></div></td><td>uint</td><td></td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">factor</div></div></td><td>double</td><td>the result is multiplied by this factor, set -1 to subtract the field</td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">setSigmasToZero</div></div></td><td>boolean</td><td>set variances to zero, should be used by adding back reference fields</td></tr>
</table>

<h2 id="fromParametrization">FromParametrization</h2><p>
Reads a solution vector from file <a class="groops-class" href="fileFormat_matrix.html">inputfileSolution</a>
which may be computed by a least squares adjustment (e.g. by <a class="groops-program" href="NormalsSolverVCE.html">NormalsSolverVCE</a>).
The coefficients of the vector are interpreted from position <strong class="groops-config-element">indexStart</strong>
(counting from zero) with help of <a class="groops-class" href="parametrizationGravityType.html">parametrizationGravity</a>.
If the solution file contains solution of several right hand sides you can choose
one with number <strong class="groops-config-element">rightSide</strong> (counting from zero).
You can also read a vector from file <a class="groops-class" href="fileFormat_matrix.html">inputfileSigmax</a>
containing the accuracies of the coefficients.</p><p>The computed result is multiplied with <strong class="groops-config-element">factor</strong>.
</p>
<table class="table table-hover">
<tr class="table-primary"><th>Name</th><th>Type</th><th>Annotation</th></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset-unbounded">parametrization</div></div></td><td><a href="parametrizationGravityType.html">parametrizationGravity</a></td><td></td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset">inputfileSolution</div></div></td><td>filename</td><td>solution vector</td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">inputfileSigmax</div></div></td><td>filename</td><td>standards deviations or covariance matrix of the solution</td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">indexStart</div></div></td><td>uint</td><td>position in the solution vector</td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">rightSide</div></div></td><td>uint</td><td>if solution contains several right hand sides, select one</td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">factor</div></div></td><td>double</td><td>the result is multiplied by this factor, set -1 to subtract the field</td></tr>
</table>

<h2 id="timeSplines">TimeSplines</h2><p>
Read a time variable gravity field from file
<a class="groops-class" href="fileFormat_timeSplinesGravityField.html">inputfileTimeSplinesGravityfield</a>
represented by a spherical harmonics expansion in the spatial domain and spline functions
in the time domain. If set the expansion is limited in the range between
<strong class="groops-config-element">minDegree</strong> and <strong class="groops-config-element">maxDegree</strong> inclusivly.</p><p>This file can be created for example by <a class="groops-program" href="Gravityfield2TimeSplines.html">Gravityfield2TimeSplines</a> or
<a class="groops-program" href="PotentialCoefficients2BlockMeanTimeSplines.html">PotentialCoefficients2BlockMeanTimeSplines</a>.</p><p>The computed result is multiplied with <strong class="groops-config-element">factor</strong>.
</p>
<table class="table table-hover">
<tr class="table-primary"><th>Name</th><th>Type</th><th>Annotation</th></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset">inputfileTimeSplinesGravityfield</div></div></td><td>filename</td><td></td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">inputfileTimeSplinesCovariance</div></div></td><td>filename</td><td></td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">minDegree</div></div></td><td>uint</td><td></td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">maxDegree</div></div></td><td>uint</td><td></td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">factor</div></div></td><td>double</td><td>the result is multiplied by this factor, set -1 to subtract the field</td></tr>
</table>

<h2 id="trend">Trend</h2><p>
The given <a class="groops-class" href="gravityfieldType.html">gravityfield</a> is interpreted
as trend function and the result is computed at time $t$ as follows
\[
V(\M x,t) = \frac{t-t_0}{\Delta t}V(\M x),
\]with $t_0$ is <strong class="groops-config-element">timeStart</strong> and $\Delta t$ is <strong class="groops-config-element">timeStep</strong>.
</p>
<table class="table table-hover">
<tr class="table-primary"><th>Name</th><th>Type</th><th>Annotation</th></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset-unbounded">gravityfield</div></div></td><td><a href="gravityfieldType.html">gravityfield</a></td><td>this field is multiplicated by (time-time0)/timeStep</td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset">timeStart</div></div></td><td>time</td><td>reference time</td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset">timeStep</div></div></td><td>time</td><td></td></tr>
</table>

<h2 id="oscillation">Oscillation</h2><p>
The given <a class="groops-class" href="gravityfieldType.html">gravityfield</a> is interpreted
as oscillation function and the result is computed at time $t$ as follows
\[
V(\M x,t) = \cos(\omega)V_{cos}(\M x)+\sin(\omega)V_{sin}(\M x),
\]with $\omega=\frac{2\pi}{T}(t-t_0)$.
</p>
<table class="table table-hover">
<tr class="table-primary"><th>Name</th><th>Type</th><th>Annotation</th></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset-unbounded">gravityfieldCos</div></div></td><td><a href="gravityfieldType.html">gravityfield</a></td><td>multiplicated by cos(2pi/T(time-time0))</td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset-unbounded">gravityfieldSin</div></div></td><td><a href="gravityfieldType.html">gravityfield</a></td><td>multiplicated by sin(2pi/T(time-time0))</td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset">time0</div></div></td><td>time</td><td>reference time</td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset">period</div></div></td><td>time</td><td>[day]</td></tr>
</table>

<h2>InInterval</h2><p>
A <a class="groops-class" href="gravityfieldType.html">gravityfield</a> is only evaluated in the interval between
<strong class="groops-config-element">timeStart</strong> inclusively and <strong class="groops-config-element">timeEnd</strong> exclusively.
Outside the interval the result is zero.</p><p>This class is useful to get a time series of monthly mean GRACE gravity field solutions.
In each month another file of potentialCoefficients is valid.
This can easily be created with <a class="groops-class" href="loopType.html">loop</a>.
</p>
<table class="table table-hover">
<tr class="table-primary"><th>Name</th><th>Type</th><th>Annotation</th></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset-unbounded">gravityfield</div></div></td><td><a href="gravityfieldType.html">gravityfield</a></td><td></td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset">timeStart</div></div></td><td>time</td><td>first point in time</td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset">timeEnd</div></div></td><td>time</td><td>last point in time will be less or equal timeEnd</td></tr>
</table>

<h2 id="tides">Tides</h2><p>
Treat <a class="groops-class" href="tidesType.html">tides</a> as gravitational forces.
The tides need a realization of <a class="groops-class" href="earthRotationType.html">earthRotation</a>
to transform between the CRF and TRF and to compute rotational deformation
from polar motion.
It also needs <a class="groops-class" href="ephemeridesType.html">ephemerides</a> from Sun, moon, and planets.
</p>
<table class="table table-hover">
<tr class="table-primary"><th>Name</th><th>Type</th><th>Annotation</th></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset-unbounded">tides</div></div></td><td><a href="tidesType.html">tides</a></td><td></td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset">earthRotation</div></div></td><td><a href="earthRotationType.html">earthRotation</a></td><td></td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">ephemerides</div></div></td><td><a href="ephemeridesType.html">ephemerides</a></td><td></td></tr>
</table>

<h2 id="topography">Topography</h2><p>
The gravity is integrated from a topographic mass distribution.
For each grid point in <a class="groops-class" href="fileFormat_griddedData.html">inputfileGridRectangular</a> a prisma with
<strong class="groops-config-element">density</strong> is assumed. The horizontal extension is computed from the grid spacing
and the vertical extension is given by <strong class="groops-config-element">radialLowerBound</strong>
and <strong class="groops-config-element">radialUpperBound</strong> above ellipsoid. All values are expressions and computed
for each point with given data in the grid file. The standard variables for grids
are available, see <a class="groops-ref" href="general.parser.html#dataVariables">dataVariables</a>.</p><p>Example: The grid file contains the orthometric height of the topography in the first
column, the geoid height in the second and the mean density of each prism in the third
column. In this case the following settings should be used:
<ul>

<li><strong class="groops-config-element">radialUpperBound</strong> = <code>data0+data1</code>,
</li><li>
<strong class="groops-config-element">radialLowerBound</strong> = <code>data1</code>,
</li><li>
<strong class="groops-config-element">density</strong> = <code>data2</code>.
</li></ul>
</p><p>As the prim computation is time consuming a maximum distance around the evaluation point
can defined with <strong class="groops-config-element">distancePrism</strong>. Afterwards a simplified radial line
(the prism mass is concentrated to a line in the center) is used up to
a distance of <strong class="groops-config-element">distanceLine</strong>. At last the prim is approximated by a point mass
in the center up to a distance <strong class="groops-config-element">distanceMax</strong> (if set). Prisms nearby the evaluation
point can be excluded with <strong class="groops-config-element">distanceMin</strong>.
</p>
<table class="table table-hover">
<tr class="table-primary"><th>Name</th><th>Type</th><th>Annotation</th></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset">inputfileGridRectangular</div></div></td><td>filename</td><td>Digital Terrain Model</td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">density</div></div></td><td>expression</td><td>expression [kg/m**3]</td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">radialUpperBound</div></div></td><td>expression</td><td>expression (variables 'height', 'data', 'L', 'B' and, 'area' are taken from the gridded data</td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">radialLowerBound</div></div></td><td>expression</td><td>expression (variables 'height', 'data', 'L', 'B' and, 'area' are taken from the gridded data</td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">distanceMin</div></div></td><td>double</td><td>[km] min. influence distance (ignore near zone)</td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">distancePrism</div></div></td><td>double</td><td>[km] max. distance for prism formular</td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">distanceLine</div></div></td><td>double</td><td>[km] max. distance for radial integration</td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">distanceMax</div></div></td><td>double</td><td>[km] max. influence distance (ignore far zone)</td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">factor</div></div></td><td>double</td><td>the result is multiplied by this factor, set -1 to subtract the field</td></tr>
</table>

<h2>EarthquakeOscillation</h2><p>
The given <a class="groops-class" href="gravityfieldType.html">gravityfield</a> is interpreted as an oscillation function
in the gravitational potential field, caused by large earthquakes.
The result is computed at time $t$ as follows:
\[
C_{lm}(\M t) = \sum_{n=0}^NC_{nlm}(1-\cos(\omega)\exp(\frac{-\omega}{2Q_{nlm}})),
\]with $\omega=\frac{2\pi}{T_{nlm}}(t-t_0)$. In this equation, $Q_{nlm}$ is the attenuation factor,
$n$ is the overtone factor, $m$ is degree, $l$ is order, and $t$ is time in second.
$T_{nlm}$ and $Q_{nlm}$ are computed with the elastic Earth model or observed from the long
period record of superconducting gravimeter measurements after the earthquakes.
</p>
<table class="table table-hover">
<tr class="table-primary"><th>Name</th><th>Type</th><th>Annotation</th></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset">inputCoefficientMatrix</div></div></td><td>filename</td><td>oscillation model parameters</td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset">time0</div></div></td><td>time</td><td>the time earthquake happened</td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">minDegree</div></div></td><td>uint</td><td></td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">maxDegree</div></div></td><td>uint</td><td></td></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">GM</div></div></td><td>double</td><td>Geocentric gravitational constant</td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">R</div></div></td><td>double</td><td>reference radius</td></tr>
</table>

<h2>Filter</h2><p>
Convert <a class="groops-class" href="gravityfieldType.html">gravityfield</a> to spherical harmonics
and <a class="groops-class" href="sphericalHarmonicsFilterType.html">filter</a> the coefficients.
</p>
<table class="table table-hover">
<tr class="table-primary"><th>Name</th><th>Type</th><th>Annotation</th></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset-unbounded">gravityfield</div></div></td><td><a href="gravityfieldType.html">gravityfield</a></td><td></td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config mustset-unbounded">filter</div></div></td><td><a href="sphericalHarmonicsFilterType.html">sphericalHarmonicsFilter</a></td><td></td></tr>
</table>

<h2 id="group">Group</h2><p>
Groups a set of <a class="groops-class" href="gravityfieldType.html">gravityfield</a> and has no further effect itself.
</p>
<table class="table table-hover">
<tr class="table-primary"><th>Name</th><th>Type</th><th>Annotation</th></tr>
<tr class="table-light"><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional-unbounded">gravityfield</div></div></td><td><a href="gravityfieldType.html">gravityfield</a></td><td></td></tr>
<tr class=""><td class="m-0"><div class="h-100 config-tree depth-0"><div class="h-100 config optional">factor</div></div></td><td>double</td><td>the result is multiplied by this factor, set -1 to subtract the field</td></tr>
</table>

        </div>
    </main>
</body>
</html>
